U.S. Pat. Nos. 1,914,938 and 4,251,947 issued, respectively, in 1932 to Boninger and in 1981 to Klawitter, teach examples of such illusion toys. The disclosures of both documents are incorporated herein by reference,
Each patent teaches a pocket watch-shape housing in which a blade in a front, windowed compartment is rotated rapidly in one direction through an arc of more than 270 degrees between rest positions on opposite sides of a through hole by a spring-biased overcenter mechanism hidden from view in a rear compartment, the blade movement being triggered by a short arcuate movement of a trigger end of an actuating lever protruding visibly from a side wall of the rear compartment, adjacent the through hole. An article modeled as a person's head (or a pin) is removably mounted with a neck thereof extending into the through hole protruding visibly through the upper compartment into the lower compartment transversely through a plane of rotation of the blade.
As start and finish positions of the short arcuate movement of the visible trigger end portion of the actuating lever are on the same opposite sides of the through hole and head/pin as the start and finish positions of the blade and, as the blade moves too quickly to be seen, the illusion is created that the blade also has moved only a short arcuate distance in the same direction as the trigger end portion of the actuating lever and, as a result, across the through hole and through the article but, astonishingly, without severing the article. In fact, the blade has not rotated the short distance across the through hole but, in an opposite direction, through the much longer complementary arc of at least 270 degrees.
Although illusion toys of the type taught by the patents noted above have been widely sold for many years they suffer from several disadvantages.
For example, the references teach location of the through hole radially inwardly of the pivotal mounting of the actuating lever or, coincidently with the pivotal mounting of the actuating lever which cannot clearly create an impression of the actuating lever actually passing across the through hole during pivotal movement to trigger the overcenter mechanism to rotate the blade.
An additional disadvantage arises from the patent teaching that the article ‘to be severed’ should not extend completely through the housing so as to visibly protrude from the rear face and, that the article is small both and inanimate, resulting in some spectators immediately suspecting that the article does not actually cross the plane of movement of the blade. A significant increase in the size of the article is precluded as the patents teach that the article receiving through hole actually passes through the part of the housing containing the mechanism, (the through hole actually passing through the aperture in the yoke or quadrant gear), precluding significant enlargement relative to the existing size of the housing.
Furthermore, the front compartment in which the blade rotates is entirely circular, visibly providing the same clearance for rotation of the blade in all directions, enabling an analytical spectator to recognize the possibility of the blade moving away from the article receiving through hole, through the much longer arc, in an opposite direction to the visible trigger end and, therefore, not crossing the article receiving through hole at all.
A further disadvantage of the entirely circular shape of the housing is that it cannot be freestanding in a stable upright position for displaying the illusion.
In addition, the overcenter mechanisms are relatively complex and/or involve a higher than optimal inertia which limits the power available for blade rotation for a given spring strength, imposing an undesirable limitation on blade size, rotational speed and, as a result, the size of the article receiving through hole.